This invention relates generally to adaptive speed control systems and particularly relates to a digital adaptive speed control for vehicles such as automobiles.
Various speed control devices for controlling the speed of a vehicle are well known in the art. Such a speed control will permit the driver to set a desired speed which is then automatically maintained by opening or closing the throttle in response to an error signal developed by the speed control.
In general such speed control systems compare the desired speed to the actual vehicle speed to derive an error or control signal. Recently digital speed control systems have become known which make use of computer techniques for developing a digital error signal. Generally the desired speed of the car is stored in a digital memory such as a counter or register. The actual speed of the vehicle as represented by a pulse train is periodically stored for a predetermined period of time in another digital register or speed counter. Now the two digital numbers are compared to generate the error signal.
While such digital speed control systems will control the vehicle speed over extended trips very precisely, they do have certain drawbacks. If the driver is not attentive he may have an accident because the car ahead of the controlled car may have a lower speed. Furthermore the known digital speed control systems only operate on the throttle of the car to either accelerate of decelerate the car by controlling the amount of fuel fed into the engine.
Various adaptive speed control systems have been proposed in the past. Some of these do not provide a digital control of either the speed or for modifying the digital speed error signal in accordance with the distance of closing speed of another car. Other anticollision devices which provide automatic control of the vehicle brakes do not include a speed control. Still other systems utilize radar as a relative speed detector only. In this case use is made of the Doppler effect which does not provide range information. Finally, it has been proposed to control trains to avoid collisions. In this case use is made of the rails as a waveguide to transmit information. Again in this proposed system there is no speed control which ties in with the radar information.
It is accordingly an object of the present invention to provide an adaptive speed control for vehicles which will modify the set speed in accordance with the closing speed and distance to a vehicle ahead of the controlled car.
A further object of the present invention is to provide an adaptive speed control of the type disclosed which actuates the brakes to avoid accidents caused by a slower car ahead of the controlled car.
Another object of the present invention is to provide such an adaptive speed control system where the braking effort is a function of the closing speed and distance of the controlled vehicle with respect to another detected vehicle.
Still a further object of the invention is to provide an adaptive speed control system for vehicles which will modify the pre-set speed in accordance with the presence of spaced roadside reflectors on a curve, thus automatically reducing the vehicle speed to a safe value for the curve.